On Thursday, the U.S. military launched 59 Tomahawk missiles at an airbase in Homs, Syria—America’s
first direct intervention against the government of Syrian President
Bashar al-Assad, whom much of the international community blames for a
chemical-weapons attack that killed some 80 Syrians earlier this week.
"It is in this vital national security interest of the United States to
prevent and deter the spread and use of deadly chemical weapons,”
President Trump told reporters Thursday evening by way of explanation.

It
was a dramatic shift for the Trump administration, which has so far
advocated—in rhetoric, if not entirely in practice—a noninterventionist
approach to foreign policy, emphasizing "America First” over
international concerns. As my colleague Jeffrey Goldberg noted,
it was also a significant departure from former President Obama’s
approach to the Syrian conflict; after a similar crisis in 2013, when
Assad was blamed for a chemical-weapons attack that killed roughly 1,000
people, Obama threatened to strike Assad but instead embraced a
negotiated deal aimed at removing the Syrian leader’s chemical arsenal.
(The attack this week showed that the deal did not achieve its stated
objective.) Meanwhile, the Trump administration has provided little
insight on what comes next, a lack of clarity that has sparked accusations
Trump acted on impulse, without a clear plan. Secretary of State Rex
Tillerson dismissed those concerns on Thursday. "I do not view it as an
emotional reaction at all,” he told reporters. So, why intervene?

"They claim deterrence—that’s very clear
both in the Department of Defense statement and the president’s
statement,” Micah Zenko, a senior fellow at the Council on Foreign
Relations, told me. That is, the strike was designed to get Assad to
stop using chemical weapons in the future. But Zenko has another theory.
"I think the unstated reason is simply punishment. It’s a demonstration
of force.”

I spoke with Zenko, who was a frequent critic of
Obama’s use of drone strikes, about the reasons countries undertake
"limited strikes” such as Thursday’s cruise missile attack in Syria. Our
conversation has been edited and condensed for clarity.

Priscilla Alvarez: What are the reasons for launching a military strike?

Micah Zenko: Punishment, deterrence, and compellence—those are the three [categories] that basically all uses of force break down into.

Punishment
is trying to hurt an adversary either in retaliation for something they
did in the past, or simply because you are tired of witnessing existing
sort of behavior and you don’t attempt to deter or compel. Your job is
just to literally physically punish an adversary or the adversary’s
capabilities.

Deterrence is to try to prevent somebody
from doing something. If you have your fist cocked and you’re about to
punch me and I say, "If you do that, then you will have this specific
credible threat or harm [to] something that you hold of value; I will
retaliate against [you] with it”—if you don’t then punch me, I have
deterred you.

Now, compellence is different and harder
because compellence is to stop somebody from doing what they’re already
doing. A great example of this is what the Obama [administration] and
now the Trump administration is trying to do with China in the South
China Sea. China is building facilities for military purposes, [and]
intelligence-gathering purposes, on disputed islands in the South China
Sea. The United States wants to compel China to change its behavior and
cease building on these disputed territories. They have not articulated a
clear threat to China if they don’t stop—and I don’t think China would
find it particularly credible anyways. But that is an example of
compellence.

We
know from academic literature that deterrence is easier than
compellence. Once a state has started doing something, it’s harder to
make them stop doing it because they have to publicly back down from an
ongoing behavior and there are audience costs for doing so—both within
its own region and again, internationally.

Alvarez: What do you think the logic behind military strikes is?

Zenko:
For the most part, states do not use force against other states for no
purpose. The logic is different from the stated objectives. And
oftentimes, the stated objectives are not the actual objectives.

For
the purposes of measurement, I just go back to those three objectives.
States don’t do things for no reason. There’s a whole literature about
diversionary foreign policy activities. If a politician or a head of
government has waning domestic political support, there’s a theory that
they will use military force abroad to "rally around the flag” and to
increase their domestic political support. In academic literature, it’s
very mixed whether or not this actually happens and whether the "rally
around the flag” effect occurs. It does occur to some extent, like
polling numbers go up, but that’s pretty temporary.

There
are lots of reasons states use force, but the key is to really
identify—to the best extent you can in the absence of reading people’s
minds—why are they actually doing it, what do they actually hope to
achieve, and how can you evaluate the wisdom and the likelihood of that
happening. And that’s a really tough goal.

Alvarez: You’ve mentioned that in the 36 cases of limited U.S. strikes you’ve studied, the U.S. has achieved its military goals just over half of the time. Under what circumstances do governments achieve military goals through the use of limited strikes?

Zenko: When
you kill somebody, when it’s strictly a targeted killing—that’s a very
demonstrable, measurable example [of a limited strike achieving its
military goal]. But as I detail very exhaustively in my book, there’s
always inevitable problems with targeting intelligence, with weather,
with weaponeering.

Also, adversaries who know they’re
going to be targeted adapt as a result. They disperse their forces, they
camouflage them, they conceal them, and they intermingle among civilian
populations to protect them from large-scale strikes. There’s lot of
different ways that targeted adversaries will adjust when they know
they’re potentially going to be struck.

Alvarez: And when do military strikes achieve political goals?

Zenko: The
one, clear-cut case of success [I studied for the United States] was in
June 1993, the U.S. put about 12 cruise missiles into the Iraqi
intelligence headquarters in Baghdad. They did this in retaliation for
an alleged plot to kill President George H.W. Bush in Kuwait City 70
days earlier. The articulated goal was to deter the Iraqi government
from exporting terrorism, or from attempting additional attacks against
U.S. officials or against U.S. personnel. By all accounts, [the Iraqis]
did not try to do that again. That’s a clear case where the use of
force—and again there are lots of other reasons why states do or don’t
do things—but we have this one intervening variable which is the use of
force and it achieved its intended political objective of deterring the
Iraqi government from sponsoring additional attempts of terrorism
against U.S. personnel.

Alvarez: What do you say to the idea of military action being used to "send a message”?

Zenko: This
is a sort of an unstated reason why forces often are used. People never
press policy makers to articulate what they exactly mean, but what they
usually mean is to try to—without defining it—compel some change in
behavior. Or they’re trying to establish—or reestablish—U.S. credibility
both against the targeted adversary and against international
audiences.

All governments, when they use military
force, give a buffet of justifications. Most of those justifications are
hard to evaluate. It speaks to different audiences. Trump used the word
"vital national security interest” [Thursday] but then he used a lot of
emotive humanitarian language to appeal to people in support of
humanitarian interventions. Secretary of State Rex Tillerson made the
point of emphasizing "decisive action” so he’s trying to enhance the
authority of the president. There’s always a range of justifications and
motives that are presented in order to get political support.

Alvarez: What about the fear of punishment? Does that sometimes motivate decision makers in international affairs?

Zenko:
I think it does. In the strikes [Thursday], I’d say punishment is the
unstated reason. Individuals, pundits, policymakers, government
officials, who have been watching this brutal, internationalized civil
war for seven years—they just become tired of it, they become exhausted
of witnessing the suffering, with the perception that America is "doing
nothing.” They just want to strike, but they don’t want to put U.S.
forces at risk and they don’t really want to alter the battlefield
calculation. And so, standoff cruise missile strikes are a great way to
punish without raising the cost or the consequences—both with U.S.
forces or to change the outcome of the civil war. I think that’s a
common reason of supporting such operations.

Alvarez: What are some possible outcomes from Thursday night’s military strike against Syria?

Zenko: The
outcomes will inevitably be a deepening of U.S. military involvement in
the civil war. The real goal is to one, punish Assad and hopefully,
deter him from undertaking additional attacks against civilians whether
with chemical weapons or not. Of course, he’ll do whatever he needs to
protect his regime as well as his patrons from Tehran and Moscow. Trump
will then recognize this and perceive the operation to have been an
ineffective long-term tactic. He may perceive that U.S. "credibility” is
on the line [and want] to do something again, and then you have to
raise the stakes and the lethality of the strikes. And then you have to
again decide to go after the patrons of the Assad regime—Russia or
Iran—or you have to continue one-off strikes.

Alvarez: So
of the reasons you cited for striking—deterrence, punishment, or
compellence—which do think motivated the Trump administration?

Zenko: They
claim deterrence—that’s very clear both in the Department of Defense
statement and the president’s statement. I think the unstated reason is
simply punishment. It’s a demonstration of force. I give them credit for
the fact that it’s limited, targeted against this airfield that the
Syrian military has used—and it’s well documented for more than a half a
decade of the Syrian air forces’ brutal and indiscriminate and really
inhumane use of airpower. You couldn’t have targeted a better, more
deserving regime asset to send that message. Fifty-nine cruise missiles
is a lot, but for an airfield that size it’s really not that
significant, and my suspicion is it’s not going to be the last time the
regime is attacked.